Explain the Python Lists

ICSM Computer 1119 18 Sep 2025

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Updated 18 Sep 2025

1 Answers

ICSM Computer 18 Sep 2025

A list is an ordered, mutable collection of items. Lists can hold different data types (integers, strings, floats, even other lists).

Defined with square brackets [].

fruits = ["apple", "banana", "cherry"]
numbers = [1, 2, 3, 4, 5]
mixed = [1, "hello", 3.14, True]
nested = [[1, 2], [3, 4]]

Basic Operations

# Create a list
my_list = [10, 20, 30, 40]

# Access elements (index starts at 0)
print(my_list[0])   # 10
print(my_list[-1])  # 40 (last element)

# Slicing
print(my_list[1:3])   # [20, 30]
print(my_list[:2])    # [10, 20]
print(my_list[2:])    # [30, 40]

# Update element
my_list[1] = 25
print(my_list)   # [10, 25, 30, 40]

List Methods

numbers = [1, 2, 3]

numbers.append(4)        # [1, 2, 3, 4]
numbers.insert(1, 10)    # [1, 10, 2, 3, 4]
numbers.extend([5, 6])   # [1, 10, 2, 3, 4, 5, 6]

numbers.remove(10)       # remove value 10
numbers.pop()            # removes last element
numbers.pop(1)           # removes element at index 1

print(numbers.index(3))  # find index of 3
print(numbers.count(2))  # count occurrences of 2

numbers.sort()           # sort ascending
numbers.reverse()        # reverse order

numbers.clear()          # empty the list

Useful Built-in Functions with Lists

nums = [3, 1, 4, 2]

print(len(nums))     # 4
print(sum(nums))     # 10
print(min(nums))     # 1
print(max(nums))     # 4
print(sorted(nums))  # [1, 2, 3, 4]

Iterating Over Lists

fruits = ["apple", "banana", "cherry"]

for f in fruits:
    print(f)

for i, f in enumerate(fruits):
    print(i, f)

List Comprehensions (Pythonic way to build lists)

# Create a list of squares
squares = [x**2 for x in range(5)]
print(squares)   # [0, 1, 4, 9, 16]

# Filter values
even_numbers = [x for x in range(10) if x % 2 == 0]
print(even_numbers)  # [0, 2, 4, 6, 8]

Summary:

List = ordered, mutable collection.
Supports indexing, slicing, adding, removing, sorting.
Powerful with list comprehensions.

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